Method and apparatus for cutting sheet material

ABSTRACT

A method and apparatus for cutting parts, patterns, or the like from fabrics, paper or other thin sheet material employing a rotary cutting tool which is supported for movement above a work surface of a penetrable supporting bed. The rotary cutting tool is carried by a numerically controlled translating mechanism which moves it over the work surface in two orthogonal coordinate directions. The tool is rotated at a peripheral speed substantially greater than the translation speed and has a peripheral cutting edge which performs the cutting operation while the tool is translated with a segment of the peripheral cutting edge penetrating through the sheet material supported on the work surface and into the penetrable supporting bed. The rotation of the tool is coordinated with the translation of the tool so that the leading edge of the tool rotates downwardly into the sheet material during the cutting operation. The cutting tool is suspended from the translating mechanism by an adjustable mount and a follower guide or foot that travels over the sheet material with the tool is connected to the adjustable mount and positions the mount so that the segment of the peripheral cutting edge penetrating through the sheet material into the penetrable supporting bed maintains a substantially constant penetration depth regardless of uneveness or variation in height of the penetrable bed.

United States Patent [1 1 [111 3,776,072

Gerber et al. 1 Dec. 4, 1973 METHOD AND APPARATUS FOR CUTTING [57] ABSTRACT SHEET MATERIAL [75] Inventors: Heinz Joseph Gerber; David R.

Pearl; Robert J. Oswell, all of Hartford, Conn.

[73] Assignee: Gerber Garment Technology, Inc.,

East Hartford, Conn.

[22] Filed: Feb. 26, 1971 [21] Appl. No.1 119,151

[52] U.S. C1. 83/34, 83/56, 83/71, 83/374, 83/483, 83/476, 83/835, 51/206 R [51] Int. Cl B26d H18 [58] Field of Search 83/374, 19, 52, 56, v

[56] References Cited UNITED STATES PATENTS 3,477,322 11/1969 Gerber et al 83/71 3,319,500 5/1967 Wild et a1. 83/556 3,354,765 11/1967 Frey et al.... 83/71 3,186,281 6/1965 Wingen 83/469 3,496,817 2/ 1970 Staats 83/614 3,619,152 11/1971 Valof 51/206 R 1 2,771,949 11/1956 Sigoda 83/470 3,495,492 2/1970 Gerber et al... 83/374 3,522,753 8/ 1970 Schmied 83/483 X Primary ExaminerAndrew R. Juhasz A method and apparatus for cutting parts, patterns, or the like from fabrics, paper or other thin sheet material employing a rotary cutting tool which is supported for movement above a work surface of a penetrable supporting bed. The rotary cutting tool is carried by a numerically controlled translating mechanism which moves it over the work surface in two orthogonal co ordinate directions. The tool is rotated at a peripheral speed substantially greater than the translation speed and has a peripheral cutting edge which performs the cutting operation while the tool is translated with a segment of the peripheral cutting edge penetrating through the sheet material supported on the work surface and into the penetrable supporting bed. The rotation of the tool is coordinated with the translation of the tool so that the leading edge of the tool rotates downwardly into the sheet material during the cutting operation. The cutting tool is suspended from the translating mechanism by an adjustable mount and a follower guide or foot that travels over the sheet material with the tool is connected to the adjustable mount and positions the mount so that the segment of the peripheral cutting edge penetrating through the sheet material into the penetrable supporting bed maintains a substantially constant penetration depth regardless of uneveness or variation in height of the penetrable bed.

19 Claims, 8 Drawing Figures Pmmmuu: 41m 3.776372 SHEET 16? 2 INVENTORS' HE/A/Z JOSEPH GERBER DA v/p R. PEA m Attorney;

METHOD AND APPARATUS FOR CUTTING SHEET MATERIAL BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for cutting sheet material such as a fabric, paper, cardboard, thin metal or the like to produce parts, patterns or other generally two-dimensional items, and, more particularly, deals with a rotary cutting. tool which is employed to cut a single ply of sheet material or a layup of only a few plies of sheet material while the tool is guided over the material by an associated numerical controller.

Numerically controlled cutting devices for cutting sheet material are already old in the art. One such device is disclosed and more particularly described in US. Pat. No. 3,495,492, issued Feb. 17, 1970, to the same assignee as the present invention. In the patented device, a reciprocating knife is guided over a penetrable bed by a numerically controlled carriage assembly which imparts two dimensional motions to the reciprocating knife in response to commands derived by a computer from a punched tape or other suitable record or memory device. The reciprocating knife is particularly useful in cutting through multiple plies of sheet material stacked one upon the other to form a multi-ply layup. The knife is accurately guided along a cutting path which defines the outline of a particular pattern piece to be formed and cuts many pattern pieces in a single traversal of the path.

While the reciprocating knife is particularly advantageous for cutting multi-ply layups of sheet material there exists the inherent tendency of the reciprocating knife to lift the sheet material during the upstroke of the knife and this tendency makes difficult the cutting of single sheets of material or layups having only two or three plies. Additionally, the speed of translation of a reciprocating knife along the cutting path is limited due to the reciprocating motion of the knife although the speed of the cutting operation is effectively multiplied by the number of plies forming the layup. Where the number of plies is small, the number of pieces produced in any given cutting operation is proportionally reduced and therefore the effective speed of the cutting operation is proportionally reduced.

It is accordingly an object of the present invention to disclose a method and apparatus for cutting a single ply or a few plies of sheet material by means of a numerically controlled cutting tool. Furthermore, it is an object of the present invention to disclose a method and apparatus by which a numerically controlled cutting tool can be operated at high translational speeds during a cutting process.

SUMMARY OF THE INVENTION The present invention resides in a method and apparatus for cutting sheet material. The apparatus, which also functions according to the novel method of the present invention, comprises means including a penetrable bed or table defining a work surface for supporting the sheet material in a spread condition during the cutting operation; a rotary cutting tool having an axis of rotation about which the tool is rotated and a peripheral cutting edge circumscribing the axis of rotation in a plane normal to the axis of rotation; a drive means which is connected to the cutting tool for rotating the tool about the axis of. rotation; another means connected to the tool for translating the tool relative to the penetrable bed in a direction generally parallel to the work surface defined on the bed; and means for positioning the cutting tool along a line generally normal to the work surface with a segment of the peripheral cutting edge of the tool extending below the work surface into the penetrable bed so that translation of the tool with respect to the bed causes the segment which penetrates into the bed to also penetrate through sheet material supported on the bed and to cut the sheet material into pattern pieces during translation of the rotary cutting tool. The drive means includes a motor for rotating the cutting too] about its own axis of rotation in a direction which produces a downward motion of the cutting edge at the leading edge of the tool. The means for positioning the cutting toolalong a line normal to the work surface is provided with means for automatically adjusting the position of the rotary cutting tool relative to the sheet material and penetrable bed so that the tool penetrates the bed by substantially a constant amount regardless of the unevenness or variations in height of the work surface defined by the bed..

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cutting apparatus embodying the present invention.

FIG. 2 is a side elevational view of an adjustable positioning mechanismsupporting a rotary cutting tool in the cutting apparatus of FIG. 1.

FIG. 3 is a front elevational view of the adjustable positioning mechanism and rotary cutting tool shown in FIG. 2.

FIG. 4 is a sectional view through a porous penetrable bed formed from foamed plastic and shows the operation of a rotary cutting tool.

FIG. 5 is a sectional view through a porous penetrable bed formed by bristles and shows the operation of a rotary cutting tool.

FIG. 6 is a fragmentary frontal view of a rotary cutting disc having a toothed or serrated peripheral cutting edge.

FIG. 7 is a fragmentary perspective view of a rotary cutting disc having an abrasive peripheral cutting edge.

FIG. 8 is a side elevational view of an alternate embodiment of the cutting apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cutting apparatus, generally designated 10, which forms one embodiment of the present invention. The apparatus and the method by which the apparatus operates are utilized to cut parts, pattern pieces or the like from fabrics, paper, foil or other sheet materials. The apparatus is composed principally of a table 12 for supporting sheet material 14 in a spread condition, a rotary cutting tool 16 which performs a cutting operation on the sheet material, a rotary drive motor 18 connected to the tool 16 to rotate the tool during the cutting operation, a numerically controlled carriage mechanism composed of an X carriage 20 for translating the tool in the X direction, as indicated on the sheet material, and a Y carriage 22 mounted on the X carriage for translating the tool in the Y direction, also indicated on the sheet material, and an adjustable positioning mechanism 24 connected to the Y carriage 22 and supporting the tool 16 for adjustment relative to the penetrable table 12. The X carriage 20 is supported at its opposite ends on racks 26 and 28 which extend longitudinally along the table 12 and are supported by brackets 30 from the lower side of the table 12. The X carriage 20 has pinion gears (not shown) which engage the respective racks 26 and 28 and are rotated by a drive riiotor (not shown) within carriage 20 to cause the carriage to translate longitudinally back and forth over the table 12 in the X direction. The Y carriage 22 is suspended from the lateral beam of the X carriage 20 and also by a laterally extending guide rod 32 which is connected to the X carriage. The Y carriage 22 is translated relative to the X carriage 20 by means of a laterally extending lead screw 34 rotated by a Y carriage motor (not shown). A numerical control computer 36 is connected through a cable 38 to the drive motors (not shown) for the respective carriages 20 and 22 and transforms commands from a punched tape 40 into command signals which are transmitted through the cable 38 to the drive motors for the carriages to move the tool 16 along a path P which defines the perimeter of a particular pattern piece to be cut from the sheet material 14. Numerical control of a cutting tool mounted on carriages which move along two orthogonal directions respectively is already well known in the art and therefore a detailed description of the computer operation is not necessary.

Turning now to a more detailed examination of the table 12, it will be noted that the table is a horizontally disposed vacuum holddown table having a frame 50 supported by legs 52, a vacuum manifold 54 connected to the lower side of the frame 50 and communicating through the fluid ports or ducts 56 in the frame to a lower vacuum compartment 58, a supporting grid 60 within the vacuum compartment 58 and lastly, a penetrable supporting bed 62 which rests upon the grid 60 and defines a generally horizontal work surface 64 on which the sheet material 14 is supported in a spread condition for cutting. The vacuum manifold 54 is connected to a vacuum pump 70 by means of fluid conduit 72. Air within the chamber 58 is drawn through and around the grid 60 to the ports S6 where it is evacuated through the manifold 54 and pump 70. The evacuation of air from chamber 58 creates a low pressure region below the bed 62. The bed 62 is either made from a porous material or provided with a plurality of channels extending vertically through the bed to make the bed porous so that a low pressure region is generated at those portions of the work surface 64 which are covered by the sheet material 14, and the material is held tightly against the work surface without fear of slippage or motion of the material relative to the surface during the cutting operation. If the sheet material 14 is an airpervious material, it is advantageous to cover the material 14 with an air-impervious overlay sheet 76 to reduce leakage of air through the material 14 and to increase the pressure differential which holds the material 14 against the surface 64. A relative thin flexible plastic, such as polyethylene, has proven particularly satisfactory for this purpose. If desired, the compartment 58 may be divided into a number of separate compartments arranged consecutively along the longitudinal direction of the table 12 and valve mechanisms tripped by the X carriage 20 may be utilized to evacuate the individual compartments directly under the carriage 20 as the carriage translates longitudinally along the table. For a more detailed description of such a vacuum holddown table, reference may be had to US. Pat.

No. 3,495,492, issued Feb. I7, 1970, to the assignee of the present invention.

The penetrable supporting bed 62 is of more particular interest with regard to the present invention since the bed must be readily penetrated by the rotary cutting tool 16 to assure accurate and efficient cutting of the sheet material supported on its work surface 64. In one form, the bed is composed of a resilient lowdensity, cellular polyethylene plastic material which has vertical channels drilled through the material for generating a vacuum at the work surface and is installed within the frame in blocks so that regions of the work surface 64 which receive repeated or particularly heavy usage can be repaired by turning the blocks over or by replacing the old blocks with new blocks as required. Ethafoam, a product of Dow Chemical Company, has proven particularly suitable for this purpose.

As seen in FIGS. 2 and 3, the rotary cutting tool 16 is a thin disc having a peripheral cutting edge which penetrates through the overlay sheet 76, through the sheet material 14 and through the work surface 64 into the penetrable bed 62 to cut the material 14. The tool 16 is mounted coaxially to a drive shaft 80 of a rotary drive motor 82 so that the tool can be rotated about its axis of rotation and produce relative motion between the peripheral cutting edge and the sheet material 14 when power is supplied to the motor through cable 84. The drive motor 82 is suspended from a platform 88 which is fixed to a part 86 of the Y carriage 22 (FIG. 1). The Y carriage part 86 is preferably movable in the vertical direction in FIGS. 2 and 3 with respect to the remainder of the Y carriage, and provided with an associated lifting motor, so that the platform 88 with the tool 16 can be lified away from the work surface 64 on command during different stages of the cutting operation. An adjustable mount 90 connects the motor 82 and its tool 16 to the platform 88 so that the position of the tool 16 can be adjusted to some extent vertically relative to the work surface 64 without changing the vertical position of the platform 88. The adjustable mount 90 is composed of a shaft 92 which is joumaled V in the platform 88 for rotation about a vertical axis 94,

a sleeve 96 which 'is mounted concentrically on the shaft 92 and slidable vertically on the lower end of the shaft, a bushing 98 fixed to the lower end of the shaft 92 for retaining the sleeve on the shaft 92 and a cantilevered bracket 100 secured to the side of the sleeve 96. The drive motor 82 is connected to the bracket 100 by means of two clamps 102 and two clamping bolts 104 at a slight inclination to the horizontal work surface 64 so that the casing of the motor 82 clears the surface 64 when the cutting tool 16 has penetrated through the surface 64 into the bed 62. Ideally, the thin disc forming the cutting tool should have its axis of rotation extending parallelto the surface 64; however, where the axis of rotation is substantially parallel to the surface 64 as shown in FIG. 2, the cutting process can be carried out in essentially the same manner as if the axis were precisely parallel to the surface.

Since the peripheral cutting edge on the rotary cutting tool 16 circumscribes the axis of rotation of the tool and lies in a plane perpendicular to the axis of rotation, the tool 16 must be rotated about the vertical axis 94 in order to orient the tool in the proper direction for translation through the sheet material 14 while a segment of the cutting edge penetrates with the bed 62. For this purpose, an orientation drive motor is con- '5 nected in driving engagement with theibracket 100 to pivot or rotate the bracket together with the motor 82 and tool 16 about the vertical axis 94. The drive train for the orientation motor 110 is composed of a toothed pulley 112 connected to the output shaft of the motor 110, a larger toothed pulley 114 secured to the upper end of the journaled shaft 92, a toothed drive belt 116 interconnecting pulleys 112 and 114 and a torque transmitting coupling between the shaft 92 and the sleeve 96 which coupling is formed by a'torque plate 118 secured to the shaft 92 immediately-below the platform 88, a dowel pin 120 anchored in the torque plate 118 at the periphery of the plate and a guide bar 122 secured to the upper end of sleeve 96 and extending radially from the sleeve to the dowel pin 120. The projecting end of the bar 122 contains an aperture 124 through which the dowel pin 120 extends in a sliding fit. Orientation commands derived from the tape 40 through the computer 36 are supplied to the orientation motor 110 which rotates the shaft 92 and bracket 100 to orient the tool 16 in the proper direction.

A follower guide or foot 130 is secured to the outer surface of sleeve 96 by means of a mounting block 132 and two clamping bolts 134 which pass through adjustment slots 136 in the upper end of the foot 130. The clamping bolts 134 together with the block 132, sleeve 96, bracket 100 and motor 82 fix the positional relationship of the foot 130 with respect to'the cutting tool 16. The lower end of the foot 130 carries a dish-shaped foot member 138 which contains a cutout 140 in which the lower portion of the tool 16 is received at a central location of the dished shape. A compression spring 142 mounted coaxially about the dowel pin 120 between the torque plate 118 and guide bar 122 urges the adjustable mount 90 downwardly toward work surface 64 together with the foot 130 and the cutting tool 16 so that the foot member 138 rides in contact with the sheet material on surface 64. Because of the fixed positional relationship of the foot 130 and tool 16, the foot effectively senses the elevation of the work surface 64, assuming a constant thickness of the sheet material, and adjusts the mount 90 to position the tool 16 relative to the sheet material 14 and the work surface 64. The fixed positional relationship of the foot 130 and tool 16 is selected so that a segment of the peripheral cutting edge on the tool penetrates through the sheet material into the bed 62 to a preselected depth and that penetration depth remains substantially constant within the boundaries of the work surface 64 regardless of the unevenness of the work surface 64 or slight variations in the distance between the surface 64 and the carriage 22 from which the tool 16 is suspended for translation over the surface 64. For example, if the tool 16 translates to the left as seen in FIG. 3, it will pass over the hump H in the bed 62. As the foot 130 translates with the tool, the dish-shaped member 138 slides up on the hump and produces a corresponding upward displacement of the sleeve 96, the motor 82 and the tool 16 so that the penetration depth of the tool at the top of the hump will be essentially the same as that at other points along the path traversed by the tool over the material 14. If the tool 16 were to pass through the hump H without being shifted vertically by the foot 130, an increased load would be imposed on the drive motor 82 and the cutting point lying at the intersection of the peripheral cutting edge at the leading edge of the'tool would deviate slightly from the true path to be followed due to the slightly tilted position of the tool and the increased size of the segment of the peripheral cutting edge penetrating into the bed 62. In a similar respect, if the tool 16 translates to the right inFIG. 3, the foot moves downwardly intodepression D in the bed 62 and causes a corresponding downward displacement of the tool 16. If the tool 16 were not guided downwardly into the depression D by the foot, but instead translated over the depression, it is possible that the too] would actually lose contact with the work surface 64 so that the cutting action at the work surface would be interrupted and the pattempiece being cut from the material would not be completely severed from the material. The guide foot 130, therefore, improves the efficiency of the cutting tool 16 by insuring that the depth of penetration into the bed 62 remains substantially constant at each point on the work surface.

FIG. 4 shows the cutting tool 16 and a portion of the penetrable bed 62. utilized by the vacuum holddown table 12 in FIG. 1 at an enlarged scale in order to more clearly understand the details of the cutting operation where a rotary cutting tool is employed. It will be presumed that the sheet material 14 is an air-pervious fabric and therefore the air-impervious sheet 76 is shown overlying the material 14 on the work surface 64. The air channels extend vertically through the bed 62 from the lower vacuum chamber 58 (FIG. 1) and create a region of. low pressure below the sheet material 14 so that atmospheric pressure above the bed 62 forces the sheet 76 and the material 14 tightly against the work surface 64 and holds the material fixedly in a spread condition on the bed. The bed 62 is sectioned along the path transversed by the cutting tool 16 so that the segment of the peripheral cutting edge 152 which penetrates through the sheet 76 and material 14 into the bed 62 is seen as having a generally fingernail configuration. As indicated by the horizontal arrow a, the tool 16 is translating from right to left so that the lefthand half of the peripheral cutting edge 152 forms the leading edge of the tool and the right-hand half forms the trailing edge of the tool. The arrow b indicates that the tool 16 is rotated by the rotary drive motor in the counterclockwise direction as viewed and therefore the cutting edge 152 moves downwardly through the material 14 adjacent the intersection of the leading edge and the work surface 64 to generate the desired cutting action. The downward motion of the cutting edge at the leading edge of the tool tends to urge the material 14 tightly against the work surface 64 during cutting and conversely eliminates the tendency of the cutting tool to lift the material 14 which accompanies the upstroke of a reciprocating knife. The downward motion is assured by coordinating the translation and orientation of the tool with the rotation of the motor and tool and is achieved by appropriately programming the tape 40 (FIG. 1). v

In a preferred embodiment of the invention, the tool 16 is driven at a high rotational speed by the motor so that the peripheral speed of the tool or the speed of the cutting edge 152 relative to the material 14 is very high, for-example, 10,000 feet per minute, a speed equiva-' lent to that of a highspeed bandsaw. Such high relative speeds of a cutting tool are not possible with a reciprocating knife due to the large inertial loads associated with the reciprocating motion of the knife. Because of the high speed of the cutting edge, the translational speed of the tool 16 through the sheet material 14 in knife.

Wlth the cutting tool 16 being rotated about its own axis of rotation and translated along a desired cutting path through the sheet material 14 while a small segment of the peripheral cutting edge 152 penetrates through the material into the bed 62, the orientation motor 110 (FIGS. 2 and 3) maintains the cutting tool tangent to or aligned with the cutting path at the intersection of the leading edge of the tool and the material 14. For this reason, the vertical axis 94 about which the tool 16 is rotated is slightly offset from the center of the tool 16 and, more particularly, is made to pass substantially through the intersecting point of the leading edge of the tool and the material 14 as shown in FIG. 4. The tendency of the intersecting point to climb or fall on the leading edge of the tool and the accompanying shift of the intersecting point away from the vicinity of the vertical axis 94 is reduced by'maintaining the penetration depth of the tool substantially constant throughout the work surface 64. It should also be noted that appropriate control of the penetration depth of the rotary cutting tool 16 permits the area defined by the intersection of the tool and the upper surface of the material 14 to be made generally congruent with the area defined by the intersection of a reciprocating knife and the upper surface of the material. With such congruency, the cutting program or tape used with the rotary cutting tool can also be used with a reciprocating knife where the leading or cutting edge of the knife is positioned substantially coincident with the vertical axis 94.

It is desirable to program the translation of the rotary cutting tool so that the tool actually overcuts or passes beyond angled comers in the cutting path followed by the tool. In other words, if the cutting path has an angled comer with the path assuming different directions at each side of the corner, the tool is translated along the path in one direction toward the corner until it cuts slightly beyond the comer. The tool is then lifted away from the penetrable supporting bed and out of contact with the sheet material, then oriented in a new direction parallel to the other side of the angled comer, then lowered so that the tool penetrates the material 14 and bed 62 at a point at least at the comer and possibly at a point backed slightly away from the corner in the new direction to insure complete severence of the material at the comer before the tool is moved along the other side of the comer in the new direction.

FIG. discloses another type of penetrable bed which can be used in conjunction with the cutting tool 16 to perform the cutting operation. The tool 16 is suspended as shown in FIGS. 1, 2 and 3 for translation as indicated by arrow a, for rotation as indicated by arrow b, for adjustment along the vertical axis 94 to maintain constant penetration depth and for orientation about axis 94 to maintain tangency at each point on the cut ting path during the process. The table 160 which holds the sheet material 14 is composed basically of a frame 162 and a penetrable bed formed by bristles 164. The bristles 164 are supported at their lower ends in a mat 166 and project upwardly to terminal points which lie generally in a horizontal plane. A vacuum pump 168 is connected by a hose 170 through a lateral portion of the frame. 162 to reduce the air pressure in the region occupied by the bristles 164. A thin sheet of rigidizing material 172, which may be, for example, a sheet of kraft paper, is positioned in direct contact with the upper ends of the bristles 164 to provide a rigid and continuous work surface 174 on which the material 14 is spread during a cutting operation. The overlay sheet 76 is positioned on the material 14 and extends to the extreme edge of the table where it passes over a horizontal frame member 176. The sheet 76 fonns a vacuum seal over the bristles 164 as well as over the sheet material 14. When the vacuum pump 168 is turned on and air surrounding the bristles is evacuated, atmospheric pressure above the table 160 forces the sheet material 14 tightly against the work surface 174 and the cutting process is carried out by means of tool 16 in essentially the same manner as that described with respect to FIG. 4. A segment of the peripheral cutting edge 152 penetrates through the sheet 76, material 14 and paper 172 into the bristles 164; however, the cutting action of the tool 16 does not damage the bristles to the same extent as that experienced with the foamed plastic fonning bed 62. The cutting of the tool through the sheet 76, material 14 and paper 172 allows a very small quantity of air to leak into the region of the bristles from above the table; however, the vacuum pump 168 can be sized to easily handle such leakages.

The rotary cutting tool and its peripheral cutting edge may take various forms. The tool 16 as shown in FIGS. 1-5 is a thin disc and has a sharp peripheral knife edge which extends smoothly and continuously about the rotational axis of the tool. The size of the rotary cutting tool can be varied and is preferably kept as small as possible, in order to minimize the length of the segment penetrating into the penetrable bed, while maintaining a depth of penetration which insures cutting of the sheet material on the work surface regardless of small bumps or depressions in the work surface. Preferably the peripheral cutting edge should lie within a circle having a diameter no less than one-half inch and no greater than 1% inches.

In FIG. 6, a rotary cutting tool takes the form of a thin wheel or disc and has a central mounting hole 182 and a serrated peripheral cutting edge formed by a plurality of serrations or small teeth 184 extending radially from the wheel. The teeth 184 produce a cutting action in sheet materials in much the same manner as the teeth of a saw blade.

In FIG. 7, another embodiment of the cutting tool is shown in a fragmentary perspective view. The tool is a disc having a central mounting hole 192 and an abrasive peripheral cutting edge 194. The abrasive edge 194 can be formed by depositing fine particles such as diamond dust or other hard particles on the periphery of the disc or by a coarse grinding process which effectively roughens the peripheral region of the disc. The abrasive rotary cutting tool 190 when rotated at high speeds relative to a sheet material performs a frictional cutting process in contrast to the severing performed by a knife-edged tool; however, both of the tools are considered to perform what is termed a cutting process within the meaning of this specification.

FIG. 8 shows an alternate embodiment of the cutting apparatus in which the foot also serves as a mounting bracket for the rotary cutting tool and the tool is rotated by a flexible, torquetransmitting drive cable. The construction of the rotatable shaft 92 and sleeve 96 is the same as that in FIGS. 2 and 3 and the connections between these members are broken awayfor the sake of clarity. The foot 200 is mounted directly to a lateral surface of the sleeve 96 by means of mounting bolts 202. At the lower end of the foot 200, a dish-shaped member 204 defines a centrally located cutout 206 through which the vertical axis 94 passes and a bushing 208 is mounted within the member 204 adjacent to the cutout 206. A rotary cutting tool 216 formed by a disc having a sharpened peripheral cutting edge is received within the cutout. A flexible, torque-transmitting drive cable 210 includes an external casing 212, which is secured in the lower end of the foot 200, and a central flexible shaft 214 which rotates within the casing and engages the bushing 208 to serve as an axle for mounting and rotating the rotary cutting tool 216 within the cutout 206. The shaft 214 is connected at its upper end to the drive shaft of a motor (not shown) which may be mounted at a remote location on thetorque plate 118 in FIGS. 2 and 3, or on the Y carriage 22 in FIG. 1, provided that the revolutions of shaft 92 and sleeve 96 are limited. The tool 216 is received within the cutout 206 so that a segment of its peripheral cutting edge extends below the dish-shaped member 204 and penetrates through the material 14 into the penetrable bed 16. Since the flexible cable 210 requires less clearance than the motor 82 of FIGS. 2 and 3, the cutting tool 16 is supported more precisely in a vertical position with respect to the work surface 64 of the bed 62. The flexible drive cable 210 is quite versatile and allows the cutting tool to be oriented about the vertical axis 94 and shifted or adjusted vertically along the axis 94.

Although the method and apparatus for cutting sheet material have been described in several different embodiments, it will be readily understood by those skilled in the art that various substitutions and modifications can be had without departing from the spirit of the invention. For example, the design of the peripheral cut ting edge of the rotary cutting tool can be varied to take forms other than those specifically disclosed by the drawings. The adjustable mount 90 which permits the tool to be adjusted vertically and rotated about axis 94 may be constructed by a splined shaft and sleeve which produce equivalent operations. The method of cutting the sheet material by rotating the leading edge of the cutting tool downwardly into the material is the preferred method; however, the cutting process may be carried out at the trailing edge of the tool provided that the method by which the material is held on the work surface is compatible with such procedure. Accordingly, the present invention has been described in several difierent embodiments merely by way of illustra-' tion rather than limitation.

We claim:

1. Apparatus for cutting sheet material having a support bed defining a work surface for supporting the sheet material in a spread condition, a tool mount, a carriage mechanism for transporting the tool mount and the support bed relative to one another in directions parallel to the work surface, a journal member between the carriage mechanism and the tool mount to permit pivoting of the mount about an axis perpendicular to the work surface, a controlled drive mechanism for regulating the transporting movements of the carriage mechanism and the pivoting movements of the tool mount, wherein the improvement comprises: a rotary cutting tool having an axis of rotation and a peripheral cutting portion circumscribing the axis of rotation; drive means connected to the rotary cutting tool for rotating the peripheral cutting portion of the tool about the axis of rotation; adjustable means connecting the tool with its axis of rotation substantially parallel to the work surface to the tool mount for rotation with the mount and adjustment relative to the mount along the axis perpendicular to the work surface; and follower means mounted in fixed relationship with the tool adjacent the tool and connecting with the adjustable means for sensing the level of the sheet material immediately surrounding the tool and maintaining the tool at a fixed position along the axis perpendicular to the work surface relative to the sheet material surrounding the tool.

2. Apparatus for cutting sheet material as defined in claim 1 wherein the adjustable means mounted adjacent the rotary cutting tool comprises a foot having a cutout.

3. Apparatus for cutting sheet material as defined in claim 1 wherein the drive means comprises a motor having a drive shaft connected to the rotary cutting tool coaxially of the axis of rotation of the tool.

4. Apparatus for cutting sheet material as defined in claim 1 wherein the drive means comprises a motor and a flexible, torque-transmitting drive cable connected between the motor and the rotary cutting tool.

5. Apparatus for cuttingsheet material as defined in claim 1 wherein said rotary cutting tool comprises a disc having a peripheral cutting edge.

6. Apparatus for cutting sheetmaterial as defined in claim 5 wherein said disc has a sharp peripheral knife edge.

7. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has an abrasive peripheral cutting edge. I

8. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has a serrated peripheral cutting edge. a

9. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has a peripheral cutting edge lying within a circle having a diameter no less than onehalf inch and no greater than 1% inches.

10. Apparatus for cutting sheet material comprising: a support bed defining a work surface for supporting sheet material in a spread condition; a rotary cutting disc having an axis of rotation about the work surface and a peripheral cutting edge; means for translating the cutting disc and the support bed relative to one another along a cutting path with the disc substantially perpendicular to the work surface and the leading peripheral cutting edge of the disc in cutting engagement with the sheet material supported on the work surface; drive means connected to the disc for rotating the disc in a given direction about the axis of rotation and independent of the translation of the disc and support bed relative to one another; means for orienting the cutting disc I about an axis perpendicular to the work surface and the sheet material supported thereon whereby the cutting.

disc exerts downward pressure on the sheet material at the point of cutting engagement therewith tourge the sheet material toward the support surface at the point of cutting engagement.

1 1. Apparatus for cutting sheet material as defined in claim wherein the support bed is a penetrable bed; and means for controlling the positioning of the cutting disc along the axis perpendicular to the work surface are provided to cause a segment of the peripheral cutting edge to extend below the work surface into the penetrable bed.

12. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is composed of a bristled mat.

13. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is composed of a foamed plastic material.

14. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is an air-pervious bed.

15. A method of cutting sheet material in which the material is spread on the work surface of a supporting bed and a cutting tool and the sheet material are controllably translated relative to one another in cutting relationship and oriented relative to one another about an axis perpendicular to the work surface so that a line of cut in the material is followed tangentially by the tool, wherein the improvement comprises: providing a cutting tool in the form of a rotary cutting disc having an axis of rotation and peripheral cutting edge; driving the cutting disc rotatably in a given direction about the axis of rotation to generate relative movement between the peripheral cutting edge and the sheet material, while the tool and sheet material are translated and oriented relative to one another to advance the tool tangentially along the line of cut; sensing the level of the sheet material in the area immediately surrounding the cutting disc; and adjusting the height of the cutting disc along the axis perpendicular to the work surface in response to the sensed level of the sheet material to maintain a predetermined segment of the peripheral cutting edge on the disc in the sheet material.

16. The method of cutting sheet material as defined in claim 15 including the additional step of coordinating the direction of the driving of the disc about the axis of rotation with the orientation and translation of the tool along the cutting path to cause the disc at the leading cutting edge to rotate downwardly toward the sheet material and the work surface.

17. The method of cutting sheet material on a penetrable supporting bed as defined in claim 15 wherein the step of adjusting further comprises causing the predetermined segment of the peripheral cutting edge on the disc to pass through both the sheet material and work surface into the penetrable bed during the cutting operation.

18. A method of cutting sheet material comprising: providing a support bed defining a work surface for supporting the sheet material in a spread condition; positioning the sheet material to be cut on the work surface of the bed; providing a rotary cutting disc having an axis of rotation above the bed and a peripheral cutting' edge circumscribing the axis; translating the rotary cutting disc and the sheet material on the work surface relative to one another along a cutting path while the cutting tool is simultaneously oriented in the direction of translation with the leading peripheral cutting edge thereof in cutting engagement with the sheet material; driving the cutting disc rotatably in a given direction about the axis of rotation independently of the translation of the disc and sheet material relative to one another; and coordinating the orienting of the cutting disc and the direction of rotation of the cutting disc about the axis of rotation relative to the advancing movement of the cutting disc along the cutting path in accordance with a predetermined program to rotate the leading peripheral cutting edge of the disc in a downward direction toward the bed and into and through the sheet material supported thereon whereby the cutting disc exerts downward pressure on the sheet material at the point of cutting engagrnent therewith to urge the sheet material toward the support surface at the point of cutting engagement.

19. A method of cutting sheet material as defined in claim 18 wherein the step of providing a support bed comprises providing a bed having a penetrable work surface; and wherein an additional step comprises causing the rotating cutting tool to penetrate through the sheet material and the work surface to a regulated depth below the work surface as the tool and sheet material translate in cutting engagement relative to one another.

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1. Apparatus for cutting sheet material having a support bed defining a work surface for supporting the sheet material in a spread condition, a tool mount, a carriage mechanism for transporting the tool mount and the support bed relative to one another in directions parallel to the work surface, a journal member between the carriage mechanism and the tool mount to permit pivoting of the mount about an axis perpendicular to the work surface, a controlled drive mechanism for regulating the transporting movements of the carriage mechanism and the pivoting movements of the tool mount, wherein the improvement comprises: a rotary cutting tool having an axis of rotation and a peripheral cutting portion circumscribing the axis of rotation; drive means connected to the rotary cutting tool for rotating the peripheral cutting portion of the tool about the axis of rotation; adjustable means connecting the tool with its axis of rotation substantially parallel to the work surface to the tool mount for rotation with the mount and adjustment relative to the mount along the axis perpendicular to the work surface; and follower means mounted in fixed relationship with the tool adjacent the tool and connecting with the adjustable means for sensing the level of the sheet material immediately surrounding the tool and maintaining the tool at a fixed position along the axis perpendicular to the work surface relative to the sheet material surrounding the tool.
 2. Apparatus for cutting sheet material as defined in claim 1 wherein the adjustable means mounted adjacent the rotary cutting tool comprises a foot having a cutout.
 3. Apparatus for cutting sheet material as defined in claim 1 wherein the drive means comprises a motor having a drive shaft connected to the rotary cutting tool coaxially of the axis of rotation of the tool.
 4. Apparatus for cutting sheet material as defined in claim 1 wherein the drive means comprises a motor and a flexible, torque-transmitting drive cable connected between the motor and the rotary cutting tool.
 5. Apparatus for cutting sheet material as defined in claim 1 wherein said rotary cutting tool comprises a disc having a peripheral cutting edge.
 6. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has a sharp peripheral knife edge.
 7. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has an abrasive peripheral cutting edge.
 8. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has a serrated peripheral cutting eDge.
 9. Apparatus for cutting sheet material as defined in claim 5 wherein said disc has a peripheral cutting edge lying within a circle having a diameter no less than one-half inch and no greater than 1 1/2 inches.
 10. Apparatus for cutting sheet material comprising: a support bed defining a work surface for supporting sheet material in a spread condition; a rotary cutting disc having an axis of rotation about the work surface and a peripheral cutting edge; means for translating the cutting disc and the support bed relative to one another along a cutting path with the disc substantially perpendicular to the work surface and the leading peripheral cutting edge of the disc in cutting engagement with the sheet material supported on the work surface; drive means connected to the disc for rotating the disc in a given direction about the axis of rotation and independent of the translation of the disc and support bed relative to one another; means for orienting the cutting disc about an axis perpendicular to the work surface and the sheet material on the surface; and program means for coordinating the orientation of the cutting disc about the perpendicular axis and the direction of rotation of the cutting disc about the axis of rotation relative to the advancing movement of the cutting disc along the cutting path through the sheet material to rotate the leading peripheral cutting edge of the disc in a downward direction toward the bed and into and through the sheet material supported thereon whereby the cutting disc exerts downward pressure on the sheet material at the point of cutting engagement therewith to urge the sheet material toward the support surface at the point of cutting engagement.
 11. Apparatus for cutting sheet material as defined in claim 10 wherein the support bed is a penetrable bed; and means for controlling the positioning of the cutting disc along the axis perpendicular to the work surface are provided to cause a segment of the peripheral cutting edge to extend below the work surface into the penetrable bed.
 12. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is composed of a bristled mat.
 13. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is composed of a foamed plastic material.
 14. Apparatus for cutting sheet material as defined in claim 11 wherein said penetrable bed is an air-pervious bed.
 15. A method of cutting sheet material in which the material is spread on the work surface of a supporting bed and a cutting tool and the sheet material are controllably translated relative to one another in cutting relationship and oriented relative to one another about an axis perpendicular to the work surface so that a line of cut in the material is followed tangentially by the tool, wherein the improvement comprises: providing a cutting tool in the form of a rotary cutting disc having an axis of rotation and peripheral cutting edge; driving the cutting disc rotatably in a given direction about the axis of rotation to generate relative movement between the peripheral cutting edge and the sheet material, while the tool and sheet material are translated and oriented relative to one another to advance the tool tangentially along the line of cut; sensing the level of the sheet material in the area immediately surrounding the cutting disc; and adjusting the height of the cutting disc along the axis perpendicular to the work surface in response to the sensed level of the sheet material to maintain a predetermined segment of the peripheral cutting edge on the disc in the sheet material.
 16. The method of cutting sheet material as defined in claim 15 including the additional step of coordinating the direction of the driving of the disc about the axis of rotation with the orientation and translation of the tool along the cutting path to cause the disc at the leading cutting edge to rotate downwardly toward the sheet material and the work surface.
 17. The method of cutting sheet material on a penetrable supporting bed as defined in claim 15 wherein the step of adjusting further comprises causing the predetermined segment of the peripheral cutting edge on the disc to pass through both the sheet material and work surface into the penetrable bed during the cutting operation.
 18. A method of cutting sheet material comprising: providing a support bed defining a work surface for supporting the sheet material in a spread condition; positioning the sheet material to be cut on the work surface of the bed; providing a rotary cutting disc having an axis of rotation above the bed and a peripheral cutting edge circumscribing the axis; translating the rotary cutting disc and the sheet material on the work surface relative to one another along a cutting path while the cutting tool is simultaneously oriented in the direction of translation with the leading peripheral cutting edge thereof in cutting engagement with the sheet material; driving the cutting disc rotatably in a given direction about the axis of rotation independently of the translation of the disc and sheet material relative to one another; and coordinating the orienting of the cutting disc and the direction of rotation of the cutting disc about the axis of rotation relative to the advancing movement of the cutting disc along the cutting path in accordance with a predetermined program to rotate the leading peripheral cutting edge of the disc in a downward direction toward the bed and into and through the sheet material supported thereon whereby the cutting disc exerts downward pressure on the sheet material at the point of cutting engagment therewith to urge the sheet material toward the support surface at the point of cutting engagement.
 19. A method of cutting sheet material as defined in claim 18 wherein the step of providing a support bed comprises providing a bed having a penetrable work surface; and wherein an additional step comprises causing the rotating cutting tool to penetrate through the sheet material and the work surface to a regulated depth below the work surface as the tool and sheet material translate in cutting engagement relative to one another. 